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Abstract Background Artificial Intelligence entails the application of computer algorithms to the huge and heterogeneous amount of morphodynamic data produced by Time-Lapse Technology. In this context, Machine Learning (ML) methods were developed in order to assist embryologists with automatized and objective predictive models able to standardize human embryo assessment. In this study, we aimed at developing a novel ML-based strategy to identify relevant patterns associated with the prediction of blastocyst development stage on day 5. Methods We retrospectively analysed the morphokinetics of 575 embryos obtained from 80 women who underwent IVF at our Unit. Embryo morphokinetics was registered using the Geri plus® time-lapse system. Overall, 30 clinical, morphological and morphokinetic variables related to women and embryos were recorded and combined. Some embryos reached the expanded blastocyst stage on day 5 (BL Group, n = 210), some others did not (nBL Group, n = 365). Results The novel EmbryoMLSelection framework was developed following four-steps: Feature Selection, Rules Extraction, Rules Selection and Rules Evaluation. Six rules composed by a combination of 8 variables were finally selected, and provided a predictive power described by an AUC of 0.84 and an accuracy of 81%. Conclusions We provided herein a new feature-signature able to identify with an high performance embryos with the best developmental competence to reach the expanded blastocyst stage on day 5. Clear and clinically relevant cut-offs were identified for each considered variable, providing an objective tool for early embryo developmental assessment.

Abstract Ovarian follicular development and ovulation are complex and tightly regulated processes that involve regulation by microRNAs (miRNAs). We previously identified differentially expressed mRNAs between human cumulus granulosa cells (CGCs) from immature early antral follicles (germinal vesicle - GV) and mature preovulatory follicles (metaphase II - M2). In this study, we performed an integrated analysis of the transcriptome and miRNome in CGCs obtained from the GV cumulus-oocyte complex (COC) obtained from IVM and M2 COC obtained from IVF. A total of 43 differentially expressed miRNAs were identified. Using Ingenuity IPA analysis, we identified 7288 potential miRNA-regulated target genes. Two hundred thirty-four of these target genes were also found in our previously generated ovulatory gene library while exhibiting anti-correlated expression to the identified miRNAs. IPA pathway analysis suggested that miR-21 and FOXM1 cooperatively inhibit CDC25A, TOP2A and PRC1. We identified a mechanism for the temporary inhibition of VEGF during ovulation by TGFB1, miR-16-5p and miR-34a-5p. The linkage bioinformatics analysis between the libraries of the coding genes from our preliminary study with the newly generated library of regulatory miRNAs provides us a comprehensive, integrated overview of the miRNA-mRNA co-regulatory networks that may play a key role in controlling post-transcriptomic regulation of the ovulatory process.

BACKGROUND: Recently described slow-cooling cryopreservation protocols involving elevated sucrose concentration have improved survival frequencies of human oocytes, potentially overcoming a major hurdle that has limited the adoption of oocyte storage. Because implantation rates of embryos from frozen oocytes remain generally low, it is still debated whether, irrespective of survival rates, this form of cryopreservation leads inevitably to the disruption or complete loss of the metaphase II (MII) spindle. METHODS: Human oocytes with an extruded polar body I (PBI) were cryopreserved using a slow-cooling method including 1.5 mol/l propane-1,2-diol (PrOH) and alternative sucrose concentrations (either 0.1 or 0.3 mol/l) in the freezing solution. Fresh control and frozen-thawed survived oocytes were analysed by confocal microscopy to evaluate MII spindle and chromosome organizations. RESULTS: Of the 104 oocytes included in the unfrozen group, 76 (73.1%) displayed normal bipolar spindles with equatorially aligned chromosomes. Spindle and chromatin organizations were significantly affected (50.8%) after cryopreservation involving lower sucrose concentration (61 oocytes), whereas these parameters were unchanged (69.7%) using the 0.3 mol/l sucrose protocol (152 oocytes). CONCLUSIONS: Partial disruption of the MII spindle and associated chromosomes accompanies inadequate cryopreservation during slow cooling. However, protocols adopting higher sucrose concentration in the freezing solution promote the retention of an intact chromosome segregation apparatus comparable in incidence to freshly collected oocytes. [ABSTRACT FROM AUTHOR]

BACKGROUND: Recently, interest in oocyte cryopreservation has steadily increased. Newly developed protocols have dramatically improved survival rates, removing perhaps the major hurdle that has prevented this approach from becoming a fully established form of treatment. However, the clinical efficiency of these protocols has not been exhaustively explored and therefore remains controversial. METHODS: Morphologically normal oocytes displaying the first polar body were frozen–thawed with a slow cooling protocol that utilized 1.5 mol/l propane-1,2-diol (PrOH) and 0.3 mol/l sucrose. RESULTS: A total of 927 oocytes from 146 patients were frozen–thawed, achieving a 74.1% survival rate. Over 76% of microinjected oocytes displayed two pronuclei 16 h post-insemination, while the proportion of embryos at 44–46 h post-insemination was 90.2%. At this time point, the majority (68.3%) of embryos were at the two-cell stage, showing in most cases (78.7%) minimal or moderate fragmentation. Eighteen clinical pregnancies, three of which were twin, were observed, giving rise to rates of 12.3 and 9.7%, calculated per patient and per embryo transfer, respectively.The implantation rate was 5.2%. To date, four children have been born and three pregnancies resulted in spontaneous abortions, while the remaining pregnancies are ongoing. CONCLUSIONS: Our data indicate that although the combination of slow cooling and high sucrose concentration ensures high rates of oocyte survival, it is not sufficient to guarantee a high standard of clinical efficiency. [ABSTRACT FROM AUTHOR]

BACKGROUND: Despite the recent increase in pregnancies from cryopreserved human oocytes, success in terms of births per thawed oocyte is still poor. Modifications to cryopreservation protocols have not been based on measurement of the osmotic response of oocytes, and methodologies are often poorly described or protocols not strictly adhered to, inevitably resulting in variability. METHODS: Volume change of mature human oocytes was measured on exposure to cryoprotectant. Oocytes were exposed to either 0.75?mol/l propane-1,2-diol (PrOH) for 10?min; 1.5?mol/l PrOH for 10?min, having been exposed to 0.75?mol/l PrOH for 7.5?min; or 1.5?mol/l PrOH plus 0.2 or 0.3?mol/l sucrose for 10?min, having been exposed to 1.5?mol/l PrOH for 10?min. RESULTS: On exposure to PrOH alone, oocytes shrank and then re-expanded, having reached 75 and 84% of their starting volume in 0.75 and 1.5?mol/l, respectively. Oocytes shrank continuously in PrOH plus sucrose, reaching 67 or 55% of their initial volume in 0.2 or 0.3?mol/l sucrose, respectively. CONCLUSIONS: To improve consistency following cryopreservation, protocols must be strictly adhered to; small changes in duration of exposure to cryoprotectant can result in drastic changes in cellular hydration and thus the fate of the cell during freezing/thawing. [ABSTRACT FROM AUTHOR]

BACKGROUND: One of the major concerns derived from the cryopreservation of meiotically mature oocytes is possible damage to the cytoskeletal apparatus, and in particular the meiotic spindle. METHODS: One hundred fresh oocytes showing the polar body I and high meiotic spindle birefringence (maximum retardance1.5?mol/l SD=2.580.1?nm), assessed through analysis, were included in this study. Oocytes were cryopreserved with a 1.5mol/l 1,2-propanediol +0.3?mol/l sucrose solution. After thawing, spindles were imaged at 0, 3 and 5?h. Spindle birefringence was quantified by measuring microtubule maximum retardance. Signals of thawed oocytes were classified as absent (non-detectable), weak (1.550.3?nm) or high (2.500.2?nm). RESULTS: Immediately after thawing, only 22.9% of oocytes showed a weak birefringence signal, while only 1.2% of oocytes displayed a high signal. Three hours after thawing, the proportion of oocytes exhibiting a weak or high intensity signal was 49.4% and 18.1%, respectively. Finally, after culture for 5?h following thawing, a weak birefringence signal was detected in 51.8% of oocytes, while 24.1% showed a high signal. There was a statistically significant increase in signal restoration after 3?h of culture (P<0.001). CONCLUSIONS: These results suggest that in mature oocytes stored via slow freezing, the meiotic spindle undergoes transient disappearance immediately after thawing but is reorganized in the majority of oocytes, at least to some extent, after 35?h of culture. [ABSTRACT FROM AUTHOR]

BACKGROUND: In this study, we compared the relative ability of FSH (100?mIU/ml), epidermal growth factor (EGF) (10?ng/ml), and follicular-fluid meiosis-activating sterol (FF-MAS, 10?mol/l) to induce meiotic resumption and polar body I (PBI) extrusion in mouse oocytes. METHODS: Cumulus-enclosed oocytes (CEO) were co-incubated with meiosis-arresting agents, including 4?mmol/l hypoxanthine (Hx), 0.3?mmol/l dibutyryl cAMP (dbcAMP), and 8.5?mol/l cilostamide, a selective inhibitor of the oocyte-specific phosphodiesterase 3 (PDE 3). RESULTS: In Hx-treated oocytes, FSH, EGF and FF-MAS induced meiosis resumption at very high rates, but only FSH and EGF also promoted PBI extrusion with high frequency. In experiments conducted in the presence of dbcAMP, FF-MAS was unable to promote an increase in germinal vesicle breakdown (GVBD) rate, whereas FSH and EGF generated a response similar to the Hx groups. Neither FSH, EGF nor FF-MAS caused any change in the meiotic status of CEO when meiotic arrest at the germinal vesicle (GV) stage was maintained by cilostamide. In the presence of Hx, naked oocytes (NkO) co-cultured with their cumulus cells were able to respond to the GVBD-inducing effect of FSH and EGF by resuming meiosis at high rate. CONCLUSIONS: Collectively, these results indicate that: (i) a signal triggered in cumulus cells by either FSH or EGF, but not necessarily coincident with FF-MAS, may contribute to meiotic maturation, supporting GVBD and extrusion of PBI; (ii) the transmission of this signal can occur in a paracrine fashion, at least with reference to the breakdown of the GV. It also appears that concomitant regulation of intra-oocyte cAMP degradation is a prerequisite for meiosis resumption. [ABSTRACT FROM AUTHOR]

BACKGROUND: Pituitary suppression by depot GnRH agonist may be excessive for ovarian stimulation in assisted reproduction technology. This study compares the efficacy of standard and half-dose depot triptorelin in a long protocol. METHODS: A total of 180 patients were randomized into two groups using sealed envelopes. Pituitary desensitization was obtained in group 1 (90 patients) with half-dose (1.87 mg) triptorelin depot in the mid-luteal phase of their menstrual cycle, and in group 2 (90 patients) with full-dose (3.75 mg) triptorelin. RESULTS: There was no premature LH surge, with LH levels being lower in the full-dose group (1.04±0.05 versus 0.7±0.06 IU/l on the day of hCG). The number of FSH ampoules used was lower in group 1 (42±2 versus 59±3). The numbers of mature oocytes (10.1±0.54 versus 7.4±0.55), of fertilized oocytes (8.24±0.35 versus 6.34±0.37) and of embryos (7.8±0.36 versus 5.9±0.37) were significantly higher in group 1. No significant differences were found in pregnancy (38.8 versus 25.3%), implantation (22.6 versus 13.8%) or abortion (6.1 versus 5.0%) rates. Cumulative pregnancy (fresh plus frozen embryo transfers: 56.8 versus 35.4%) rate was significantly higher in group 1. CONCLUSION: A half-dose of depot triptorelin can be successfully used in ovarian stimulation for IVF and produce a higher number of good quality embryos with a good chance of implantation. [ABSTRACT FROM AUTHOR]

BACKGROUND To develop novel cryopreservation methods, we estimated the permeability coefficients Lp (hydraulic conductivity) and PEG (cryoprotectant permeability) of mature human oocytes after exposure to ethylene glycol (EG) and tested the efficiency of a multi-step slow cooling protocol based on this cryoprotectant. METHODS Oocytes were perfused with 1.5 mol/l EG for 10 min. Oocyte volume at each time point was calculated and normalized to the original volume. Slow cooling was conducted by exposing oocytes to increasing EG concentrations (0.5, 1.0 and 1.5 mol/l n = 155) or 1.5 mol/l of propane-1,2-diol (PrOH) n = 102. Oocytes which survived cryopreservation n = 80 and fresh oocytes n = 73 were prepared for confocal microscopy analysis of the meiotic spindle. RESULTS During EG exposure, oocytes underwent an abrupt 50% volume reduction. Complete recovery of the initial volume was not observed. From the values of a best fit plot, the coefficients Lp = 0.82 ± 0.29 µm min−1 atm−1 (mean ± SD) and PEG 0.10 ± 0.01 µm s−1 were generated. Survival rates after freezing with EG were lower than with PrOH (51.6 versus 71.5%, respectively, P P CONCLUSIONS The oocyte plasmalemma possesses limited permeability to EG and EG exposure causes considerable osmotic stress. However, post-thaw rates of survival and normal meiotic spindle organization may be preserved by protocols which are designed in order to minimize osmotic stress. [ABSTRACT FROM AUTHOR]

BACKGROUND We studied the ultrastructural characteristics of human mature oocytes frozen/thawed (F/T) using different concentrations of sucrose. Fresh human mature oocytes were used as controls. METHODS The oocytes (n = 48) were fixed in 1.5% glutaraldehyde at sampling (n = 16) or after freeze/thawing performed using a slow cooling method with propane-1,2-diol 1.5 mol/l and sucrose at either 0.1 mol/l (n = 16) or 0.3 mol/l (n = 16) in the freezing solution. The oocytes were then processed for electron microscopy observations. RESULTS Fresh and F/T oocytes belonging to both study groups were regularly rounded in sections, with a homogeneous cytoplasm and an intact zona pellucida (ZP). Organelles (mainly mitochondria–smooth endoplasmic reticulum aggregates and mitochondria–vesicle complexes) were abundant and uniformly dispersed in the ooplasm. The amount and density of cortical granules appeared to be abnormally reduced in some F/T samples, independently of the sucrose concentration in the freezing solution: this feature was frequently associated with an increased density of the inner ZP, possibly related to the occurrence of zona ‘hardening’. Furthermore, slight to moderate microvacuolization was revealed in the ooplasm of some F/T oocytes, particularly in those treated with sucrose 0.3 mol/l. CONCLUSIONS Freeze/thawing procedures are associated with ultrastructural alterations in specific oocyte microdomains, presumably linked to the reduced developmental potential of mature cryopreserved oocytes. Further work is needed to determine whether or not a high concentration of sucrose plays a role, at least in part, in producing the above alterations. [ABSTRACT FROM AUTHOR]

BACKGROUND: The relationship between early embryo post-implantation development in couples undergoing assisted reproductive techniques (ARTs) and sperm chromatin alterations has not been satisfactorily explained. The aim of this study was to assess the relationship between sperm DNA fragmentation in IVF/ICSI patients, sperm parameters (concentration, motility and morphology) and ART outcome, especially with regard to clinical pregnancy and pregnancy loss (spontaneous miscarriage or biochemical pregnancy). METHODS: DNA fragmentation was evaluated by TUNEL assay, performed on sperm suspensions after density gradient separation, in 132 men undergoing an ART cycle (82 IVF and 50 ICSI) and correlated with sperm parameters and ART outcome. RESULTS: A highly significant negative correlation was found between DNA fragmentation and sperm parameters. There was a close relationship between DNA fragmentation and post-implantation development in ICSI patients: the clinical pregnancy and pregnancy loss rates significantly differed between patients with high and low sperm DNA fragmentation (P = 0.007 and P = 0.009, respectively). CONCLUSIONS: Sperm DNA fragmentation seems to affect embryo post-implantation development in ICSI procedures: high sperm DNA fragmentation can compromise ‘embryo viability’, resulting in pregnancy loss. [ABSTRACT FROM AUTHOR]

Study Question: Can more reliable time cut-offs of embryo developmental incompetence be generated by combining time-lapse technology (TLT), artificial intelligence, and preimplantation genetics screening for aneuploidy (PGT-A)?, Summary Answer: Embryo developmental incompetence can be better predicted by time cut-offs at multiple developmental stages and for different ranges of maternal age., What Is Known Already: TLT is instrumental for the continual and undisturbed observation of embryo development. It has produced morphokinetic algorithms aimed at selecting embryos able to generate a viable pregnancy, however, such efforts have had limited success. Regardless, the potential of this technology for improving multiple aspects of the IVF process remains considerable. Specifically, TLT could be harnessed to discriminate developmentally incompetent embryos: i.e. those unable to develop to the blastocyst stage or affected by full-chromosome meiotic aneuploidies. If proven valuable, this application would prevent the non-productive use of such embryos, thereby improving laboratory and clinical efficiency and reducing patient stress and costs due to unnecessary embryo transfer and cryopreservation., Study Design, Size, Duration: The training dataset involved embryos of PGT-A cycles cultured in Embryoscope with a single media (836 euploid and 1179 aneuploid blastocysts and 1874 arrested embryos; 2013-2020). Selection criteria were ejaculated sperm, own (not donated) fresh oocytes, trophectoderm biopsy and comprehensive-chromosome-testing to diagnose uniform aneuploidies. Out-of-sample (30% of training), internal (299 euploid and 490 aneuploid blastocysts and 680 arrested embryos; 2021-2022) and external (97 euploid, 110 aneuploid and 603 untested blastocysts and 514 arrested embryos, 2018 to early 2022) validations were conducted., Participants/materials, Setting, Methods: A training dataset (70%) was used to define thresholds. Several models were generated by fitting outcomes to each timing (tPNa-t8) and maternal age. ROC curves pinpointed in-sample classification values associated with 95%, 99% and 99.99% true-positive rate for predicting incompetence. These values were integrated with upper limits of maternal age ranges (<35, 35-37, 38-40, 41-42, and >42 years) in logit functions to identify time cut-offs, whose accuracy was tested on the validation datasets through confusion matrices., Main Results and the Role of Chance: For developmental (in)competence, the best performing (i) tPNa cut-offs were 27.8 hpi (error-rate: 0/743), 32.6 hpi (error rate: 0/934), 26.8 hpi (error rate: 0/1178), 22.9 hpi (error-rate: 1/654, 0.1%) and 17.2 hpi (error rate: 4/423, 0.9%) in the <35, 35-37, 38-40, 41-42, and >42 years groups, respectively; (ii) tPNf cut-offs were 36.7 hpi (error rate: 0/738), 47.9 hpi (error rate: 0/921), 45.6 hpi (error rate: 1/1156, 0.1%), 44.1 hpi (error rate: 0/647) and 41.8 hpi (error rate: 0/417); (iii) t2 cut-offs were 50.9 hpi (error rate: 0/724), 49 hpi (error rate: 0/915), 47.1 hpi (error rate: 0/1146), 45.8 hpi (error rate: 0/636) and 43.9 hpi (error rate: 0/416); (iv) t4 cut-offs were 66.9 hpi (error rate: 0/683), 80.7 hpi (error rate: 0/836), 77.1 hpi (error rate: 0/1063), 74.7 hpi (error rate: 0/590) and 71.2 hpi (error rate: 0/389); and (v) t8 cut-offs were 118.1 hpi (error rate: 0/619), 110.6 hpi (error rate: 0/772), 140 hpi (error rate: 0/969), 135 hpi (error rate: 0/533) and 127.5 hpi (error rate: 0/355). tPNf and t2 showed a significant association with chromosomal (in)competence, also when adjusted for maternal age. Nevertheless, the relevant cut-offs were found to perform less well and were redundant compared with the blastocyst development cut-offs., Limitations, Reasons for Caution: Study limits are its retrospective design and the datasets being unbalanced towards advanced maternal age cases. The potential effects of abnormal cleavage patterns were not assessed. Larger sample sizes and external validations in other clinical settings are warranted., Wider Implications of the Findings: If confirmed by independent studies, this approach could significantly improve the efficiency of ART, by reducing the workload and patient impacts (extended culture and cleavage stage cryopreservation or transfer) associated with embryos that ultimately are developmentally incompetent and should not be considered for treatment. Pending validation, these data might be applied also in static embryo observation settings., Study Funding/competing Interest(s): This study was supported by the participating institutions. The authors have no conflicts of interest to declare., Trial Registration Number: N/A., (© The Author(s) 2024. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Purpose: Recent evidence showed that the phase between pronuclear fading and the first cleavage is a perilous bridge connecting the zygote and the embryo. Indeed, delay in the short interval between pronuclear breakdown (PNBD) and the first cytokinesis may result in chromosome segregation errors. We tested the hypothesis that delays in this final phase of fertilization are associated with a detrimental impact on embryo development., Methods: This is a retrospective study of 1315 zygotes cultured using time lapse technologies generated in 205 first ICSI-cycles., Results: We observed an association between increasing times of the pronuclear fading-first cleavage interval (t2-tPNf) and the rates of trichotomous/direct unequal cleavage at the first (DUC-1) and second (DUC-2) mitotic cycle. Moreover, we observed a reduced blastulation rate. No significant associations were observed between rates of direct unequal cleavage at the third mitotic cycle (DUC-3) and top-quality blastocysts, euploidy, and live births. To evaluate whether the interval t2-tPNf could have a predictive value for the onset of DUC-1 and DUC-2, ROC curve analyses were performed. The area under the curve values obtained for DUC-1 showed a significant prediction accuracy. The best cut-offs to identify zygotes with a high risk of DUC-1 and DUC-2 occurrence were t2-tPNf > 2.78 (hours) and t2-tPNf > 2.50 (hours), respectively., Conclusion: Delay in the short interval between PNBD and the first cytokinesis result in trichotomous cleavage and early developmental arrest. However, if the embryos reach the blastocyst stage, rates of euploidy and live birth do not appear to be compromised., Competing Interests: Declarations. Conflict of interest: The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Oocyte loss, a natural process that accelerates as women approach their mid-30s, poses a significant challenge to female reproduction. Recent studies have identified DNA damage as a primary contributor to oocyte loss, but the mechanisms underlying DNA damage accumulation remain unclear. Here, we show that aged oocytes have a lower DNA repair capacity and reduced mobility of DNA damage sites compared to young oocytes. Incomplete DNA repair in aged oocytes results in defective chromosome integrity and partitioning, thereby compromising oocyte quality. We found that DNA repair proteins are arranged in spatially distinct DNA repair compartments that form during the late stages of oocyte growth, accompanied by changes in the activity of DNA repair pathways. We demonstrate alterations in these compartments with age, including substantial changes in the levels of key DNA repair proteins and a shift toward error-prone DNA repair pathways. In addition, we show that reduced cohesin levels make aged oocytes more vulnerable to persistent DNA damage and cause changes in DNA repair compartments. Our study links DNA damage accumulation in aged oocytes, a leading cause of oocyte loss, to cohesin deterioration and changes in the organization, abundance, and response of DNA repair machinery., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objective: To assess whether segmental aneuploid embryos display unique morphokinetic patterns., Design: Retrospective multicenter study including a total of 7,027 embryos cultured between 2016 and 2021 in three European in vitro fertilization centers. Analysis was performed on aggregated multicenter data and separately for data from each center. Embryos with no more than four chromosomal alterations were considered in the analysis, resulting in 3,040 euploids and 2,818 whole-chromosome and 697 segmental aneuploids. Overall, the data set contained 3,742 distinct euploid-segmental sibling pairs., Setting: In vitro fertilization clinics., Patient(s): Standard morphokinetic features were annotated using various time-lapse systems. Blastocysts were subjected to comprehensive chromosomal screening via preimplantation genetic testing for aneuploidy., Intervention(s): Morphokinetic patterns were compared among euploid, whole-chromosome aneuploid, and segmental aneuploid embryos., Main Outcome Measure(s): Morphokinetic timings across groups were compared using statistical analysis, and associations with cleavage features were assessed. Multicenter and center-specific multivariate logistic regression models were calibrated, and their predictive performance was evaluated on independent test set data using area under the receiver operating characteristic curve (AUROC) metrics., Result(s): Segmental aneuploid embryos cleaved significantly slower than their euploid siblings across the first three cell cycles, with a delay reaching the blastocyst-stage of development. Specifically during these early cell cycles, segmental aneuploid embryos were also shown to be significantly slower than their aneuploid siblings. A logistic model on the basis of morphokinetic data from the multicenter data set and regressed against type of aneuploidy displayed modest predictive performance on an independent test set (train-AUROC = 0.58; test-AUROC = 0.57). Predictive performance improved on the basis of data from a single center displaying adequate predictive performance on an independent test set from the same center (train-AUROC = 0.74; test-AUROC = 0.64). However, the predictive value diminished when tested on data from other centers (AUROC = 0.52-0.55). Finally, the presence of multinucleation and blastomere exclusion at the cleavage stage were associated with segmental aneuploidies. The combination of morphokinetic features and these discrete embryo morphological features into the logistic regression model (train-AUROC = 0.71) provided an improved prediction of segmental aneuploidy, supporting future investigations using more comprehensive annotation systems., Conclusion(s): The developed predictive framework may help improve decision-making in preimplantation genetic testing for aneuploidy cycles, helping in the evaluation of embryos showing segmental aneuploidy and distinguishing which embryos are more likely to not have lethal uniform aneuploidies for transfer., Competing Interests: Declaration of Interests M.F. has nothing to disclose. L.B. reports funding from CIAPOT/2022/23 postdoctoral contract, outside the submitted work. C.S.O. has nothing to disclose. L.P. reports honoraria Ferring Pharmaceuticals lecture at elevate congress 2024 and full-time employee at Juno Genetics. S.C. is an employee of Juno Genetics. M.R. has nothing to disclose. M.P. has nothing to disclose. A.C. reports consulting fees from Gedeon Richter and Cooper Surgical; honoraria from Kitazato, Gedeon Richter, Cooper Surgical, and Merck; travel support from Vitrolife and Genea; Human Fertilisation and Embryology Authority Scientific and Clinical Advances Advisory Committee; Alpha Scientists in Reproductive Medicine ALPHA Vice President of this nonprofit society; and minor shareholder of Care Fertility, outside the submitted work. R.S. has nothing to disclose. G.C. has nothing to disclose. D.C. reports personal fees from Merck KGaA, IBSA, Organon, and Fairtility, outside the submitted work. L.F.R. reports personal fees from Merck KGaA, MSD, Ferring, IBSA, Cooper Surgical, Cook, Medea, Nterilizer, and Fujifilm-Irvine Scientific, outside the submitted work. M.M. reports personal fees as honoraria for lectures from Merck, Vitrolife, MSD, Ferring, AIVF, Theramex, Gideon Richter, Genea Bimedix, and Life Whisperer. A.C. is a full-time employee of Juno Genetics., (Copyright © 2024 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

Cell cycle regulation is crucial to assure expansion of a cell population, while preserving genome integrity. This notion is especially relevant to fertilization and early embryo development, a time when the cell cycle transforms from meiotic into mitotic cycles. Zygote-to-embryo transition is acutely error-prone, causing major developmental perturbations, including cleavage delays, tri- and multi-chotomous cleavages, and cell fragmentation. Another such alteration is bi- and multinucleation, consisting of the simultaneous formation of two or more nuclei at interphase. Indeed, multinucleation affects a large proportion of early human embryos, typically at the two-cell stage. Mechanistically, several factors, including spindle dysfunction, failed cleavage, and cell fusion, may generate this cell anomaly. In assisted reproduction treatment, multinucleation is associated with reduced developmental rates and lower implantation rates in Days 2-3 embryo transfers. However, many multinucleated embryos can develop to the blastocyst stage. In blastocyst transfers, the current evidence does not suggest a major impact of a previous history of multinucleation on the odds of euploidy or successful treatment outcomes. Human embryo multinucleation remains a not-fully-understood but developmentally relevant and intriguing phenomenon which requires further research of its generative mechanisms and clinical implications., (© The Author(s) 2024. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Study Question: What are the implications of the presence cytoplasmic strings (Cyt-S) and their quantity and dynamics for the pre-implantation development of human blastocysts?, Summary Answer: Cyt-S are common in human embryos and are associated with faster blastocyst development, larger expansion, and better morphological quality., What Is Known Already: Cyt-S are dynamic cellular projections connecting inner cell mass and trophectoderm (TE) cells, that can be observed during blastocyst expansion. Their prevalence in human embryos has been estimated to be between 44% and 93%. Data relevant to their clinical implications and role in development are lacking, limited, or controversial., Study Design, Size, Duration: Retrospective study conducted at a single IVF center between May 2013 and November 2014 and involving 124 pre-implantation genetic testing for aneuploidy cycles in a time-lapse incubator with ≥1 blastocyst biopsied and vitrified (N = 370 embryos assessed). These cycles resulted in 87 vitrified-warmed single-euploid blastocyst transfers., Participants/materials, Setting, Methods: ICSI, continuous blastocyst culture (Days 5-7), TE biopsy of fully expanded blastocysts without Day 3 zona pellucida drilling, qPCR to assess uniform full-chromosome aneuploidies, and vitrification were all performed. Only vitrified-warmed euploid single-embryo-transfers were conducted. Blastocyst morphological quality was defined according to Gardner's criteria. The AI-based software CHLOE™ (Fairtility) automatically registered timings from time of starting blastulation (tSB) to biopsy (t-biopsy, i.e. blastocyst full-expansion) as hours-post-insemination (hpi), embryo area (including zona pellucida in µm2), and spontaneous blastocyst collapses. One senior embryologist manually annotated Cyt-S presence, quantity, timings, and type (thick cell-to-cell connections and/or threads). All significant associations were confirmed through regression analyses. All couples', cycles', and embryos' main features were also tested for associations with Cyt-S presence, quantity, and dynamics., Main Results and the Role of Chance: About 94.3% of the patients (N = 117/124) had ≥1 embryo with Cyt-S. Out of a total of 370 blastocysts, 55 degenerated between blastulation and full-expansion (N = 55/370, 14.9%). The degeneration rate among embryos with ≥1 Cyt-S was 10.8% (N = 33/304), significantly lower than that of embryos without Cyt-S (33.3%, N = 22/66, P < 0.01). Of the remaining 315 viable blastocysts analyzed, 86% (N = 271/315; P < 0.01) had ≥1 Cyt-S, on average 3.5 ± 2.1 per embryo ranging 1-13. The first Cyt-S per viable embryo appeared at 115.3 ± 12.5 hpi (85.7-157.7), corresponding to 10.5 ± 5.8 h (0.5-31) after tSB. Overall, we analyzed 937 Cyt-S showing a mean duration of 3.8 ± 2.7 h (0.3-20.9). Cyt-S were mostly threads (N = 508/937, 54.2%) or thick cell-to-cell connections becoming threads (N = 382/937, 40.8%) than thick bridges (N = 47/937, 5.0%). The presence and quantity of Cyt-S were significantly associated with developmentally faster (on average 6-12 h faster) and more expanded (on average 2700 µm2-larger blastocyst's area at t-biopsy) embryos. Also, the presence and duration of Cyt-S were associated with better morphology. Lastly, while euploidy rates were comparable between blastocysts with and without Cyt-S, all euploid blastocysts transferred from the latter group failed to implant (N = 10)., Limitations, Reasons for Caution: Cyt-S presence and dynamics were assessed manually on seven focal planes from video frames recorded every 15 min. The patients included were mostly of advanced maternal age. Only associations could be reported, but no causations/consequences. Lastly, larger datasets are required to better assess Cyt-S associations with clinical outcomes., Wider Implications of the Findings: Cyt-S are common during human blastocyst expansion, suggesting their physiological implication in this process. Their presence, quantity and dynamics mirror embryo viability, and morphological quality, yet their role is still unknown. Future basic science studies are encouraged to finally describe Cyt-S molecular nature and biophysical properties, and Artificial Intelligence tools should aid these studies by incorporating Cyt-S assessment., Study Funding/competing Interest(s): None., Trial Registration Number: N/A., (© The Author(s) 2024. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Competing Interests: All authors declare the receipt of honoraria and support for attending meetings associated with this work from Gedeon Richter.

Purpose: The continuous improvement and development of fertility care, internationally, requires ongoing monitoring of current delivery processes and outcomes in clinical practice. This descriptive and exploratory mixed-methods study was conducted in eight countries (Brazil, China, France, Germany, Italy, Mexico, Spain and the United Kingdom) to assess the unmet needs of fertility patients (male and female), and existing challenges, barriers and educational gaps of physicians and laboratory specialists involved in human fertility care during the COVID-19 pandemic., Materials and Methods: The study was deployed sequentially in two phases: 1) in-depth 45-minute semi-structured interviews (n=76), transcribed, coded and thematically analysed using an inductive reasoning approach, 2) an online survey (n=303) informed by the findings of the qualitative interviews, face validated by experts in reproductive medicine, and analysed using descriptive and inferential statistical methods., Results: The integrated results of both phases indicated numerous areas of challenges, including: 1) investigating male-related infertility; 2) deciding appropriate treatment for men and selective use of assisted reproductive technology; and 3) maintaining access to high-quality fertility care during a pandemic., Conclusions: The paper presents a reflective piece on knowledge and skills that warrant ongoing monitoring and improvement amongst reproductive medicine healthcare professionals amidst future pandemics and unanticipated health system disruptions. Moreover, these findings suggest that there is an additional need to better understand the required changes in policies and organizational processes that would facilitate access to andrology services for male infertility and specialized care, as needed., Competing Interests: None declared., (Copyright® by the International Brazilian Journal of Urology.)

IVF laboratories routinely adopt morphological pronuclear assessment at the zygote stage to identify abnormally fertilized embryos deemed unsuitable for clinical use. In essence, this is a pseudo-genetic test for ploidy motivated by the notion that biparental diploidy is required for normal human life and abnormal ploidy will lead to either failed implantation, miscarriage, or significant pregnancy complications, including molar pregnancy and chorionic carcinoma. Here, we review the literature associated with ploidy assessment of human embryos derived from zygotes displaying a pronuclear configuration other than the canonical two, and the related pregnancy outcome following transfer. We highlight that pronuclear assessment, although associated with aberrant ploidy outcomes, has a low specificity in the prediction of abnormal ploidy status in the developing embryo, while embryos deemed abnormally fertilized can yield healthy pregnancies. Therefore, this universal strategy of pronuclear assessment invariably leads to incorrect classification of over 50% of blastocysts derived from atypically pronucleated zygotes, and the systematic disposal of potentially viable embryos in IVF. To overcome this limitation of current practice, we discuss the new preimplantation genetic testing technologies that enable accurate identification of the ploidy status of preimplantation embryos and suggest a progress from morphology-based checks to molecular fertilization check as the new gold standard. This alternative molecular fertilization checking represents a possible non-incremental and controversy-free improvement to live birth rates in IVF as it adds to the pool of viable embryos available for transfer. This is especially important for the purposes of 'family building' or for poor-prognosis IVF patients where embryo numbers are often limited., (© The Author(s) 2024. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Purpose: To assess the relation between number of inseminated oocytes and cumulative live birth rate (CLBR) in order to provide guidance for limiting the number of surplus blastocysts., Methods: The study was a retrospective, single-center cohort analysis of 1223 ART complete cycles. Cycles were stratified according to female age (≤ 34, 35-38, and 39-42 years) and number of inseminated oocytes (1-5, 6-10, and > 10). Inclusion criteria were indication for IVF/ICSI with own spermatozoa and blastocyst culture up to day 6 of all embryos., Results: In patients younger than 35 years, insemination of more than ten oocytes produced an increase in overall blastocyst number, CLBR (40.3%, 54.3%, and 75.8%, respectively, for each oocyte group) and surplus embryo rate (12.9%, 27.8%, and 49.7% of cases for each group). Instead, in the middle age group, the use of more than ten oocytes was solely associated with an increase in the rate of surplus embryos (1.25%, 21.33%, and 28.68% of cases after stratification for oocyte number). In older patients, neither CLBR (9.1%, 23.9%, and 24.7%, respectively) nor rate of surplus embryos (2.0%, 7.1%, and 13.4% of cases for each group) were higher in cycles with more than ten inseminated oocytes., Conclusion: In women up to 38 years, sustainable CLBR are achieved while limiting the number of inseminated oocytes and the resulting blastocysts remaining unused. Based on this notion, novel treatment strategies could pursue high outcome rates, while alleviating the problems derived from surplus stored embryos., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Multiple pregnancies are associated with significant maternal, fetal, and neonatal risks, including prematurity, low birth weight, pre-eclampsia, anemia, postpartum hemorrhage, intrauterine growth restriction, neonatal morbidity, and increased neonatal and infant mortality rates. Assisted reproductive technology (ART) treatments should prioritize efforts to reduce such events, resisting patient demand for the transfer of multiple embryos at each transfer to increase success rates. Extended culture, embryo selection, and single blastocyst transfer can mitigate the risk of high-order multiple pregnancies. Intriguingly, elective single-embryo transfer (eSET) greatly reduces, but does not completely eliminate, the likelihood of multiple gestations. The occurrence of monozygotic twinning (MZT) gives rise to identical twins. It is more prevalent in women undergoing in vitro fertilization (IVF) compared with natural conception. In fact, the reported risks of monozygotic twinning in IVF and natural conception are 1.7 and 0.4%, respectively. The factors suspected to increase the risk of MZT in IVF are multiple embryo transfer, micromanipulation, and extended in vitro culture. Determining chorionicity and amnionicity is crucial in the assessment of multiple pregnancies during the first-trimester ultrasound examination. Dichorionic twins result from embryo splitting within 3 days after fertilization, while monochorionic twins occur when the splitting takes place between 4 and 8 days after fertilization. These timings are suggested by observations carried out in natural pregnancies. In ART, there is evidence of dichorionic twins derived from single embryo transfer (SET). Here, we report a case of dichorionic diamniotic triplets after a single blastocyst transfer occurred in our center. To our knowledge, this is the first case documented so far., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Study Question: Is embryo culture in a closed time-lapse system associated with any differences in perinatal and maternal outcomes in comparison to conventional culture and spontaneous conception?, Summary Answer: There were no significant differences between time-lapse and conventional embryo culture in preterm birth (PTB, <37 weeks), low birth weight (LBW, >2500 g) and hypertensive disorders of pregnancy for singleton deliveries, the primary outcomes of this study., What Is Known Already: Evidence from prospective trials evaluating the safety of time-lapse incubation for clinical use show similar embryo development rates, implantation rates, and ongoing pregnancy and live birth rates when compared to conventional incubation. Few studies have investigated if uninterrupted culture can alter risks of adverse perinatal outcomes presently associated with IVF when compared to conventional culture and spontaneous conceptions., Study Design, Size, Duration: This study is a Swedish population-based retrospective registry study, including 7379 singleton deliveries after fresh embryo transfer between 2013 and 2018 from selected IVF clinics. Perinatal outcomes of singletons born from time-lapse-cultured embryos were compared to singletons from embryos cultured in conventional incubators and 71 300 singletons from spontaneous conceptions. Main perinatal outcomes included PTB and LBW. Main maternal outcomes included hypertensive disorders of pregnancy (pregnancy hypertension and preeclampsia)., Participants/materials, Setting, Methods: From nine IVF clinics, 2683 singletons born after fresh embryo transfer in a time-lapse system were compared to 4696 singletons born after culture in a conventional incubator and 71 300 singletons born after spontaneous conception matched for year of birth, parity, and maternal age. Patient and treatment characteristics from IVF deliveries were cross-linked with the Swedish Medical Birth Register, Register of Birth Defects, National Patient Register and Statistics Sweden. Children born after sperm and oocyte donation cycles and after Preimplantation Genetic testing cycles were excluded. Odds ratio (OR) and adjusted OR were calculated, adjusting for relevant confounders., Main Results and the Role of Chance: In the adjusted analyses, no significant differences were found for risk of PTB (adjusted OR 1.11, 95% CI 0.87-1.41) and LBW (adjusted OR 0.86, 95% CI 0.66-1.14) or hypertensive disorders of pregnancy; preeclampsia and hypertension (adjusted OR 0.99, 95% CI 0.67-1.45 and adjusted OR 0.98, 95% CI 0.62-1.53, respectively) between time-lapse and conventional incubation systems. A significantly increased risk of PTB (adjusted OR 1.31, 95% CI 1.08-1.60) and LBW (adjusted OR 1.36, 95% CI 1.08-1.72) was found for singletons born after time-lapse incubation compared to singletons born after spontaneous conceptions. In addition, a lower risk for pregnancy hypertension (adjusted OR 0.72 95% CI 0.53-0.99) but no significant difference for preeclampsia (adjusted OR 0.87, 95% CI 0.68-1.12) was found compared to spontaneous conceptions. Subgroup analyses showed that some risks were related to the day of embryo transfer, with more adverse outcomes after blastocyst transfer in comparison to cleavage stage transfer., Limitations, Reasons for Caution: This study is retrospective in design and different clinical strategies may have been used to select specific patient groups for time-lapse versus conventional incubation. The number of patients is limited and larger datasets are required to obtain more precise estimates and adjust for possible effect of additional embryo culture variables., Wider Implications of the Findings: Embryo culture in time-lapse systems is not associated with major differences in perinatal and maternal outcomes, compared to conventional embryo culture, suggesting that this technology is an acceptable alternative for embryo incubation., Study Funding/competing Interest(s): The study was financed by a research grant from Gedeon Richter. There are no conflicts of interest for all authors to declare., Trial Registration Number: N/A., (© The Author(s) 2023. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

To investigate the potential effect of endometriosis on embryo development and clinical outcomes, a retrospective analysis of 716 women undergoing their first standard in vitro fertilization (sIVF) cycles (205 endometriosis and 511 with tubal factor infertility) was performed. The endometriosis group included women with an ultrasonographic or surgical diagnosis. Control subjects were women diagnosed with tubal factor infertility by laparoscopy or hysterosalpingogram. The primary outcome of the study was live birth. Cumulative live birth was also assessed in a subgroups analysis. After adjusting for confounders we found no significant difference in fertilization rate, blastulation, top-quality blastocyst, live birth, cumulative live birth (subgroups analysis) and miscarriage rate. In the endometriosis group, the number of retrieved oocytes was smaller (6.94 ± 4.06 Vs 7.50 ± 4.6, adjusted p < 0.05). We observed a statistically significant difference in the percentage of day-3 embryos with ≥8 blastomeres (33.12 ± 22.72 endometriosis vs, 40.77 ± 27.62 tubal factor, adjusted p < 0.01) and a negative correlation between the presence of endometriomas and a number of retrieved oocytes [B coefficient =-1.41, 95%CI (-2.31-0.51), adjusted p = 0.002]. Our results suggest that endometriosis affects the number of retrieved oocytes but not embryo development and live birth.

Study Question: Do embryologists from different European countries agree on embryo disposition decisions ('use' or 'discard') about Day 7 (>144 h post-insemination) and/or low-quality blastocysts (LQB;

Study Question: What clinical and laboratory differences emerge from parallel direct comparison of embryos reaching the blastocyst stage between Days 4, 5, 6, and 7 (Days 4-7)?, Summary Answer: Increasing times to blastocyst formation are associated with a worse clinical outcome and perturbations in developmental patterns appear as early as the fertilization stage., What Is Known Already: Previous evidence indicates that later times to blastocyst development are associated with a worse clinical outcome. However, the vast majority of these data concern Day 5 and Day 6 blastocysts, while Day 4 and Day 7 blastocysts remain less thoroughly investigated. In addition, studies comparing in parallel the developmental patterns and trajectories of Day 4-7 blastocysts are lacking. This leaves unanswered the question of when and how differences among such embryos emerge. Acquisition of such knowledge would significantly contribute to understanding the relative impact of intrinsic and extrinsic causes of embryo developmental kinetics and competence., Study Design, Size, Duration: This retrospective study involved time-lapse technology (TLT) monitoring of Day 4 (N = 70), Day 5 (N = 6147), Day 6 (N = 3243), and Day 7 (N = 149) blastocysts generated in 9450 ICSI cycles. Oocyte retrievals were carried out after clomiphene citrate-based minimal ovarian stimulation, between January 2020 and April 2021., Participants/materials, Setting, Methods: Couples included in the study presented with different diagnoses, mainly male factor and unexplained infertility. Cases involving cryopreserved gametes or surgically retrieved sperm were excluded. Microinjected oocytes were assessed by a combined TLT-culture system. Day 4-7 blastocyst groups were compared in terms of morphokinetics (pronuclear dynamics, cleavage patterns and timings, and embryo quality) and clinical outcome. Clinically usable blastocysts were cryopreserved and transferred in single vitrified-warmed blastocyst transfers (SVBT)., Main Results and the Role of Chance: From 19 846 microinjected oocytes, 17 144 zygotes (86.4%) were obtained. Overall, the blastocyst development rate was 56.0%. Rates of blastocysts formation on Days 4, 5, 6, and 7 were 0.7%, 64.0%, 33.8%, and 1.6%, respectively. The average expanded blastocyst development times were 98.4 ± 0.4, 112.4 ± 0.1, 131.6 ± 0.1, and 151.2 ± 0.5 h in the Day 4-7 groups, respectively. Female age was positively associated with longer times to blastocyst development. Rates of both inner cell mass (ICM) and trophectoderm (TE) morphological grade A blastocysts were negatively associated with the day of blastocyst development (P < 0.0001). The differences in development times and intervals increased progressively until blastocyst expansion (P < 0.0001 for all development times). Strikingly, such differences were already markedly evident as early as the time of pronuclear fading (tPNf) (20.6 ± 0.3, 22.5 ± 0.0, 24.0 ± 0.0, 25.5 ± 0.3; Days 4-7, respectively; P < 0.0001). Rates of cleavage anomalies (tri-/multi-chotomous mitosis or rapid cleavage) occurring at the first or second/third division cycles were also positively associated with longer times to blastocyst development. Implantation, ongoing pregnancy, and live birth rates were progressively reduced with increasing blastocyst development times (P < 0.0001), even after stratification for maternal age. When controlled for female age, male age, number of previous embryo transfer cycles, morphological grade of the ICM and TE, and progesterone supplementation, the probabilities of implantation, clinical, and ongoing pregnancy and live birth were significantly decreased in Day 6 blastocysts in comparison to Day 5 blastocysts. Follow-up data on birth length, weight, and malformations were comparable among the four blastocyst groups., Limitations, Reasons for Caution: The study is limited by its retrospective design. Having been obtained from a single centre, the data require independent validation., Wider Implications of the Findings: This study extends previous data on the relation between time of blastocyst formation and clinical outcome. It also indicates that differences in developmental times and patterns of Day 4-7 blastocysts occur as early as the fertilization stage, possibly dictated by intrinsic gamete-derived factors., Study Funding/competing Interest(s): This study was supported by the participating institutions. The authors have no conflict of interest to declare., Trial Registration Number: N/A., (© The Author(s) 2023. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Human embryos are very frequently affected by maternally inherited aneuploidies, which in the vast majority of cases determine developmental failure at pre- or post-implantation stages. However, recent evidence, generated by the alliance between diverse technologies now routinely employed in the IVF laboratory, has revealed a broader, more complex scenario. Aberrant patterns occurring at the cellular or molecular level can impact at multiple stages of the trajectory of development to blastocyst. In this context, fertilization is an extremely delicate phase, as it marks the transition between gametic and embryonic life. Centrosomes, essential for mitosis, are assembled ex novo from components of both parents. Very large and initially distant nuclei (the pronuclei) are brought together and positioned centrally. The overall cell arrangement is converted from being asymmetric to symmetric. The maternal and paternal chromosome sets, initially separate and scattered within their respective pronuclei, become clustered where the pronuclei juxtapose, to facilitate their assembly in the mitotic spindle. The meiotic spindle is replaced by a segregation machinery that may form as a transient or persistent dual mitotic spindle. Maternal proteins assist the decay of maternal mRNAs to allow the translation of newly synthesized zygotic transcripts. The diversity and complexity of these events, regulated in a precise temporal order and occurring in narrow time windows, make fertilization a highly error-prone process. As a consequence, at the first mitotic division, cellular or genomic integrity may be lost, with fatal consequences for embryonic development., (© The Author(s) 2023. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology.)

For more than two decades, the European IVF-Monitoring Consortium has collected data on IVF in Europe with the aim of monitoring the quality and safety of assisted reproductive technology (ART) treatments, to ensure the highest performance with the lowest risk for patients and their offspring. Likewise, the Society for Assisted Reproductive Technology in the USA and the Australia/New Zealand Assisted Reproduction Database collect, process and publish data in their regions. The better the legal framework for ART surveillance, the more complete and reliable are the datasets. Worldwide, the landscape of ART regulation is fragmented, and until there is a legal obligation to report ART data in all countries, with an appropriate quality control of the data collected, the reported outcomes should be interpreted with caution. Once uniform and harmonized data are achieved, consensus reports based on collective findings can begin to address key topics such as cycle segmentation and complications. Improved registration systems and datasets allowing optimized surveillance should be developed in collaboration with patient representatives to consider patients' needs, especially aiming to provide higher transparency around ART services. Support from national and international reproductive medicine societies will also be essential to the future evolution of ART registries., (Copyright © 2023. Published by Elsevier Ltd.)

Purpose: To investigate whether high relative humidity conditions (HC), when using a time-lapse system (TLS) with sequential culture media, are beneficial to embryo culture, improving ongoing pregnancy rates., Methods: We included patients undergoing their first ICSI cycle treatment from April 2021 to May 2022. Patients assigned to dry conditions (DC) or HC were 278 and 218, respectively. We used a GERI TLS, three chambers configured in humidity conditions and three in dry conditions. The effect of HC on ongoing pregnancy rate was assessed by the propensity matched sample, to reduce potential differences between women undergoing either HC or DC and reduce biased estimation of treatment effect., Result: After adjusting for several confounding variables and applying the propensity score (PS), no significant differences were observed in the rates of normal (2PN) and abnormal (1PN and 3PN) fertilization, blastulation, top-quality blastocysts, frozen blastocysts, ongoing pregnancies, and miscarriages. The 2-cell (t2) and 4-cell (t4) stages and cell divisions between such stages occurred earlier and were more synchronous in the in DC., Conclusion: These results suggest that HC conditions do not improve the rate of ongoing pregnancy and several embryological outcomes, under the conditions used in this study based on a time-lapse system and sequential culture with day 3 medium change-over., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)